The number of candidate compositions is nearly infinite for various useful materials, such as superconductors, zeolites, magnetic materials, phosphors, nonlinear optical materials, thermoelectric materials, high and low dielectric materials and the like. Discovery and optimization of such compositions is not trivial. Even though the chemistry of extended solids has been extensively explored, few general principles have emerged that allow one to predict with certainty the composition, structure and reaction pathways for the synthesis of such solid state compounds.
The preparation of new materials with novel and useful chemical and/or physical properties is at best unpredictable considering current levels of understanding. Consequently, the discovery of new materials depends largely on the ability to synthesize and analyze new compounds. Given approximately 100 elements in the periodic table, which can be used to make compositions consisting of three, four, five, six or more elements, the universe of possible new compounds remains largely unexplored. As such, there exists a need in the art for a more efficient, economical and systematic approach for the synthesis of novel materials and for the screening of such materials for useful properties.
Using the techniques of “combinatorial chemistry”, methods have been developed for the synthesis and screening of large libraries (up to 1014 molecules) of peptides, oligonucleotides and other small molecules. Using various state-of-the-art methods, arrays containing thousands or potentially millions of different combinations of elements can be formed. Such techniques have met with substantial success in, for example, screening various ligands such as peptides and oligonucleotides to determine their relative binding affinity to a receptor such as an antibody.
Methods of combinatorial synthesis involve substrates supporting arrays of diverse materials in predefined regions. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on the substrate to form different materials. Many classes of materials can be generated combinatorially, including, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, etc. Once prepared, such materials can be screened for useful properties including, for example, electrical, thermal, mechanical, chemical, etc. Arrays of materials with slightly varying composition, concentrations, stoichiometries and thicknesses are deposited on known locations on a substrate so that the materials can be readily synthesized and analyzed.
It will be appreciated that methods of combinatorial chemistry described to date suffer from an inherent limitation, viz., that they are mainly suited for screening materials whose intended use will be in the form of a thin film rather than a “bulk” form. Sample arrays fabricated by thin-film deposition methods cannot replicate crucial processing steps used to make bulk materials (casting, sintering, cold or hot rolling, etc.) Moreover, it is very difficult to measure many crucial properties, especially mechanical properties, in a small region on a much larger substrate and have reasonable confidence that the true properties of such a small volume of material are actually being obtained.